How to Use ReactJS with TypeScript for Strongly Typed Applications

Introduction

As React applications grow in size and complexity, maintaining code quality and catching bugs early becomes increasingly important. This is where TypeScript comes in. TypeScript is a statically typed superset of JavaScript that enhances development with type safety, auto-completion, and robust tooling.

In this article, we’ll explore how to use ReactJS with TypeScript to build strongly typed, scalable, and maintainable applications. Whether you’re migrating an existing project or starting from scratch, this guide will help you make the most of React and TypeScript together.

Why Use TypeScript with React?

🔹 Type Safety – Catch errors at compile time rather than runtime
🔹 Better Developer Experience – IDE support with autocompletion, refactoring, and tooltips
🔹 Improved Code Readability – Explicit types make code easier to understand
🔹 Scalability – Types make large codebases more maintainable

Getting Started with React and TypeScript

🔧 Create a React + TypeScript App

Use Create React App with the TypeScript template:

This sets up your project with .tsx file support and a preconfigured TypeScript environment.

Basic TypeScript Concepts in React

1. Typing Props

  name: string;
  age?: number; // Optional prop
};

const Greeting: React.FC<GreetingProps> = ({ name, age }) => (
  <h2>Hello {name}! {age && `You're ${age} years old.`}</h2>
);

2. Typing State with useState

For more complex states:

type User = {
  id: number;
  name: string;
};

const [user, setUser] = useState<User | null>(null);

3. Typing Events

Using Interfaces and Types

You can define props using type or interface.

You can also extend types:

Typing useEffect and API Calls

  const fetchData = async () => {
    const response = await fetch('https://api.example.com/data');
    const result: MyDataType = await response.json();
    setData(result);
  };

  fetchData();
}, []);

Typing Component Refs

const focusInput = () => {
  inputRef.current?.focus();
};

Typing Context API

  user: string;
  login: (name: string) => void;
};

const AuthContext = createContext<AuthContextType | undefined>(undefined);

const AuthProvider: React.FC = ({ children }) => {
  const [user, setUser] = useState('');
  const login = (name: string) => setUser(name);
  return (
    <AuthContext.Provider value={{ user, login }}>
      {children}
    </AuthContext.Provider>
  );
};

Best Practices

✅ Use explicit types for props, state, and events
✅ Prefer interface for public APIs and type for union types or aliases
✅ Create reusable types for consistency across components
✅ Avoid any—it defeats the purpose of TypeScript
✅ Use utility types like Partial, Pick, and Record to transform types
✅ Configure tsconfig.json to enable strict mode for better type checking

Common Utility Types

Conclusion

Combining ReactJS with TypeScript gives developers a powerful toolkit for building robust, scalable, and maintainable applications. With strong typing, better tooling, and a smoother development experience, TypeScript helps reduce bugs and improve code quality in modern React projects.

🔑 Key Takeaways:

• TypeScript improves type safety and developer productivity

• Use types and interfaces to define clear and consistent component contracts

• Integrate TypeScript with hooks, props, events, and context for full coverage

• Follow best practices and use utility types to reduce repetition

By embracing TypeScript in your React apps, you set your projects up for long-term success. ✅